Recording apparatus and recording method

ABSTRACT

In a recording apparatus, a recording medium is fixed to a recording medium fixing member. To record a desired image, the recording medium is exposed to light containing image/character data, while the recording medium is moved in the main scan direction, and a plurality of spots arrayed on the recording medium are moved in a direction orthogonal to the main scan direction. In the recording apparatus, first and second exposure operations are performed. In the first exposure operation, the recording medium is exposed to the light containing image/character data, while forming pixel groups or island patterns each consisting of a predetermined number of pixels consecutively arrayed on the recording medium in the main and sub-scan directions. In a second exposure operation and the subsequent ones, the pixels in an unexposed area other than the island patterns on the recording medium are successively exposed to the light.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording method and recordingapparatus for recording information, such as images and characters,particularly information, such as color images and characters usingcolor tones of K, C, M and Y colors, on a recording medium.

2. Description of the Related Art

For the recording of images and characters, there is known a recordingmethod in which an image receiving sheet and a transfer sheet arelayered one on the other, and in this state, are fixed onto a drum, andthose are exposed to laser light. In this case, the image receivingsheet is wound around the drum in a state that its image receiving layeris directed upward. The transfer sheet is wound on the drum in a statethat its toner layer is layered on the image receiving layer of theimage receiving sheet. A recording head of the laser exposure type isreciprocatively moved in directions parallel to the rotational shaft ofthe drum. The recording head emits laser light and takes the form of aplurality of spots of light when it lands on the recording medium. Theplural spots 1, as shown in FIG. 15, are linearly arrayed in the movingdirection of the recording head. In the recording method, the rotationaldirection of the drum is coincident with a main scan direction, and themoving direction of the recording head is coincident with a sub scandirection. Accordingly, when the rotational motion of the drum and thelinear motion of the recording head are combined, the transfer sheet isscanned with the spots to thereby transfer a desired image on the imagereceiving sheet.

In the recording method, optical energy of the laser light is transducedinto thermal energy by the optical-to-thermal transducing layer at arecording local area or part irradiated with the laser spots. At thistime, the heat generation is instantaneously performed, and water andorganic solvent, which are contained in the optical-to-thermaltransducing layer and the toner layer, are volatilized, and called gasis generated. Accordingly, in the recording method in which the imagereceiving sheet and the transfer sheet are layered one on the other, andan acting layer acting in connection with the laser light is sandwichedbetween those sheets, the gas generated is hard to run out into the air,and stays between the image receiving sheet and the transfer sheet.

At both ends of the spot array, the gas is easy to run out in thesub-scan direction (the right side or left side in FIG. 15). At thecentral part of the spot array, the generated gas is hard to run out inthe sub-scan direction, and it stagnates at the central part of the spotarray.

At the central part of the spot array, the generated gas is put betweenthe toner layer and the image receiving layer, so that the toner layerand the image receiving layer are not in close contact with each other.In this state, the toner layer is not transferred to the image receivinglayer even at a part of the recording medium irradiated with the laserlight. As a result, no color or thin color is formed on that part in thefinal image. When this phenomenon is observed macroscopically (by theeye), a stripe (vertical stripe) 3 appears which extends in the drumrotational direction, as shown in FIG. 15, and it will be an imagedefect.

For example, when 32 spots are arrayed at an interval of 10 μm (2450dpi), a distance between the spots located at both ends of the spotarray in the sub-scan direction, is 310 μm. In an another example where256 spots are arrayed at an interval of 10 μm (2450 dpi), a distancebetween the spots located at both ends of the spot array in the sub-scandirection, is 2550 μm. As the spot-to-spot distance between both ends ofthe spot array becomes larger, the gas is harder to run out at thecentral part, and also when it is observed by the eye, it becomes theimage unevenness and it is easily recognizable.

To be more specific, the gas stagnates at the central part of the spotarray, and the toner layer and the image receiving layer are not inclose contact with each other. In this state, heat generated in theoptical-to-thermal transducing layer of the transfer sheet does not flowto the image receiving layer; in a usual case, it flows to the latter.And heat is accumulated in the transfer sheet. The result is that theoptical-to-thermal transducing layer of the transfer sheet and the tonerlayer are heated and its temperature is higher than that in the normalstate. When the temperature rises till the optical-to-thermaltransducing layer and the toner layer are decomposed, gas is furthergenerated, and the optical-to-thermal transducing layer and the tonerlayer are molten and decomposed to thereby lose their normal state. Inthis state, an optical density at the central part is low, or theoptical-to-thermal transducing layer, which should not be transferred,is transferred onto the image receiving layer. More serious image defectoccurs.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide arecording method and recording apparatus in which the gas generated atthe recording local area does not stagnate in an already recorded areabetween the toner layer and the image receiving layer, therebypreventing the formation of the image defect resulting from the spotarray.

To achieve the above object, there is provided an image recording methodexecuted by a recording apparatus having a recording medium fixingmember for fixing a recording medium, which is formed by couplingtogether a toner layer of a transfer film as a heat mode sensitivematerial and an image receiving layer of a receiver film in a layeringmanner, and a recording head capable of irradiating the recording mediumwith a plurality of spots of light, wherein the recording head exposesthe recording medium in accordance with image/character data to therebyrecord a desired image on the recording medium, in a manner that therecording head is moved relative to the recording medium fixed to therecording medium fixing member in a main scan direction in which therecording head is moved relative to the recording medium, and theplurality of spots irradiated and arrayed on the recording medium aremoved in a sub-scan direction orthogonal to the main scan direction, theexposure operation being performed by relatively moving the recordinghead from a position near the original point of the sub-scan to aposition near the end of the sub-scan.

The image recording method thus constructed is improved in that in afirst exposure operation, which is performed by moving the recordinghead from a position near the original point of the sub-scan to aposition near the end of the sub-scan, the recording medium is exposedto the light containing information of image/character data, whileforming pixel groups (referred to as island patterns) each consisting ofa predetermined number of pixels consecutively arrayed on the recordingmedium in the main and sub-scan directions, and in a second exposureoperation and the subsequent ones, the pixels in an unexposed area otherthan the island patterns on the recording medium are successivelyexposed to the light.

According to another aspect of the invention, there is provided arecording apparatus having a recording medium fixing member for fixing arecording medium, which is formed by coupling together a toner layer ofa transfer film as a heat mode sensitive material and an image receivinglayer of a receiver film in a layering manner, and a recording headcapable of irradiating the recording medium with a plurality of spots oflight, wherein the recording head exposes the recording medium inaccordance with image/character data to thereby record a desired imageon the recording medium, in a manner that the recording head is movedrelative to the recording medium fixed to the recording medium fixingmember in a main scan direction in which the recording head is movedrelative to the recording medium, and the plurality of spots irradiatedand arrayed on the recording medium are moved in a sub-scan directionorthogonal to the main scan direction. The recording apparatus thusconstructed is improved by an exposure controller device operating suchthat in a first exposure operation, which is performed by moving therecording head from a position near the original point of the sub-scanto a position near the end of the sub-scan, the recording medium isexposed to the light containing information of image/character data,while forming pixel groups (referred to as island patterns) eachconsisting of a predetermined number of pixels consecutively arrayed onthe recording medium in the main and sub-scan directions, and in asecond exposure operation and the subsequent ones, the pixels in anunexposed area other than the island patterns on the recording mediumare successively exposed to the light.

In a preferred embodiment of the image recording apparatus, in the firstexposure operation, after the recording head reaches a position near theend of the sub-scan and returns to a position near the original point ofthe sub-scan in the first exposure operation, the pixels in theunexposed area not having been exposed in the preceding exposureoperation are exposed R times (R: positive integer).

In another preferred embodiment of the image recording apparatus, in thefirst exposure operation, after the recording head reaches the positionnear the end of the sub-scan in the first exposure operation, therecording head returns to the position near the original point of thesub-scan while exposing the pixels in the unexposed area not having beenexposed in the preceding exposure operation.

In yet another preferred embodiment of the image recording apparatus, atthe R-th exposure by the recording head, the recording head may exposethe pixels as defined by the image/character data in an area on therecording medium other than the area on the recording medium which hasbeen exposed in the first to (R−1) th exposure operations.

In still another preferred embodiment of the image recording apparatus,at the first exposure operation, a percentage of the island patterns tothe whole image/character data to be exposed is 20% to 80%.

In a further preferred embodiment of the image recording apparatus, apercentage of the pixels as defined by the image/character data in anarea on the recording medium other than the area on the recording mediumwhich has been exposed in the first to (R−1) th exposure operations, tothe whole image/character data to be exposed is 20% or higher.

According to yet another aspect of the invention, there is provided animage recording method executed by a recording apparatus having arecording medium fixing member for fixing a recording medium, which isformed by coupling together a toner layer of a transfer film as a heatmode sensitive material and an image receiving layer of a receiver filmin a layering manner, and a recording head capable of irradiating therecording medium with a plurality of spots of light, wherein therecording head exposes the recording medium in accordance withimage/character data to thereby record a desired image on the recordingmedium, in a manner that the recording head is moved relative to therecording medium fixed to the recording medium fixing member in a mainscan direction in which the recording head is moved relative to therecording medium, and the plurality of spots irradiated and arrayed onthe recording medium are moved in a sub-scan direction orthogonal to themain scan direction, the exposure operation being performed byrelatively moving the recording head from a position near the originalpoint of the sub-scan to a position near the end of the sub-scan. Theimage recording method is improved in that where the spots of light aredivided into an “n” umber of blocks (n=positive integer of 2 or larger),the recording medium is exposed by using the first block of spots, whileforming pixel groups (referred to as island patterns) each consisting ofa predetermined number of pixels consecutively arrayed on the recordingmedium in the main and sub-scan directions, and the pixels in anunexposed area other than the island patterns on the recording mediumare gradually exposed by using the 2nd to (n−1)th blocks of spots, andthe remaining pixels in the unexposed area are exposed by the n-th blockof spots.

According to still another aspect of the invention, there is provided arecording apparatus having a recording medium fixing member for fixing arecording medium, which is formed by coupling together a toner layer ofa transfer film as a heat mode sensitive material and an image receivinglayer of a receiver film in a layering manner, and a recording headcapable of irradiating the recording medium with a plurality of spots oflight, wherein the recording head exposes the recording medium inaccordance with image/character data to thereby record a desired imageon the recording medium, in a manner that the recording head is movedrelative to the recording medium fixed to the recording medium fixingmember in a main scan direction in which the recording head is movedrelative to the recording medium, and the plurality of spots irradiatedand arrayed on the recording medium are moved in a sub-scan directionorthogonal to the main scan direction, the exposure operation beingperformed by relatively moving the recording head from a position nearthe original point of the sub-scan to a position near the end of thesub-scan. The recording apparatus is improved by an exposure controllerdevice operating such that where the spots of light are divided into an“n” umber of blocks (n=positive integer of 2 or larger), the recordingmedium is exposed by using the first block of spots, while forming pixelgroups (referred to as island patterns) each consisting of apredetermined number of pixels consecutively arrayed on the recordingmedium in the main and sub-scan directions, and the pixels in anunexposed area other than the island patterns on the recording mediumare gradually exposed by using the 2nd to (n−1)th blocks of spots, andthe remaining pixels in the unexposed area are exposed by the n-th blockof spots.

In a preferred embodiment of the image recording apparatus as mentionedabove, a percentage of an unexposed part at the exposure by the firstblock of spots to the whole image/character data to be exposed is 20% to80%.

In another preferred embodiment of the image recording apparatus, apercentage of image/character data other than that exposed by the 1st to(n−1)th blocks of spots at the exposure by the n-th block of spots, tothe whole image/character data to be exposed is 20% or higher.

In yet another preferred embodiment of the image recording apparatus,the island pattern is configured to be flat or outcurved at itsdownstream side as viewed in the main scan direction.

In still another preferred embodiment of the image recording apparatus,the outcurved part of the island pattern consists of at least two pixelsconsecutively arrayed in the sub-scan direction.

In further preferred embodiment of the image recording apparatus, theisland pattern is configured to be slanted to the downstream side in thesub-scan direction, and to the upstream side in the main scan direction.

In an additional preferred embodiment of the image recording apparatus,an array of the plural island patterns is directed to the downstreamside in the sub-scan direction and to the upstream in the main scandirection.

As described above, in the recording method in which the image receivingsheet and the transfer sheet are layered one on the other, and an actinglayer acting in connection with the laser light is sandwiched betweenthose sheets, the recording medium is exposed to light containing imagedata in the form of island patterns thereon. Therefore, the followinguseful effects are produced:

-   -   a. “Gas stagnation” is removed, and image unevenness is        lessened;    -   b. The exposure method effectively operates for the image part        of which the area rate (dot %) is 70% or higher.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a recording apparatusconstructed according to the present invention,

FIG. 2 is an enlarged, perspective view showing a recording section ofthe recording apparatus,

FIG. 3 is a cross sectional view showing a structure including an imagereceiving sheet and a transfer sheet, which is used in the recordingmethod and the recording apparatus of the invention,

FIG. 4 is a diagram for conceptually showing a recording process,

FIG. 5 is a diagram useful in explaining the main scan direction,sub-scan direction, laser spot numbers, line numbers in the sub-scandirection in the recording apparatus, those items being used for anisland pattern exposure of the invention,

FIGS. 6(a) and 6(b) are diagrams showing an “island pattern exposureprocess” which forms a first embodiment of the invention, specificallyshowing an exposure state on the recording medium after a first exposureoperation is performed,

FIGS. 7(a) and 7(b) are diagrams showing an “island pattern exposureprocess” which forms the first embodiment, specifically showing anexposure state on the recording medium after a second exposure operationis performed,

FIGS. 8(a), 8(b), and 8(c) are diagrams showing a second instance of thefirst embodiment of the invention,

FIGS. 9(a), 9(b), 9(c), and 9(d) are diagrams for explaining a shape ofan island pattern not having gas stagnation, which is a secondembodiment of the invention,

FIGS. 10(a), 10(b), 10(c), and 10(d) are explanatory diagrams forexplaining an island pattern free from the pattern omission, which formsa third embodiment of the invention,

FIGS. 11(a), 11(b), 11(c), and 11(d) are explanatory diagrams forexplaining an inappropriate island pattern which blocks the flowing ofgas generated in the preceding thin-out exposure operation to theoutside of the recording medium,

FIGS. 12(a), 12(b), 12(c), and (d) are diagrams showing a fourthembodiment of the invention, which defines island patterns enabling theflowing of gas generated in the preceding thin-out exposure operation tosmoothly flow out of the recording medium,

FIG. 13 is a block diagram showing a process in which an image signalcoming from a computer is processed and an image signal to be applied tothe recording head is generated,

FIGS. 14(a), 14(b), 14(c), 14(d), and 14(e) are diagrams showing imagedata the blocks in FIG. 13,

FIG. 15 is a diagram showing an array of spots of laser light irradiatedby the conventional recording method,

FIGS. 16(a), 16(b), and 16(c) are diagrams showing exposure states onthe recording medium at the m-th to (m+2)th rotation of the drum in afirst instance of the fifth embodiment according to the invention,

FIGS. 17(a), 17(b), and 17(c) are diagrams, subsequent to FIG. 6(c),showing exposure states on the recording medium at the (m+3)th to(m+5)th rotation of the drum,

FIGS. 18(a), 18(b), and 18(c) are diagram showing exposure states on therecording medium at the m-th to (m+2)th rotation of the drum in a secondinstance of the fifth embodiment according to the invention,

FIGS. 19(a), 19(b), and 19(c) are diagrams, subsequent to FIG. 18(c),showing exposure states on the recording medium at the (m+3)th to(m+5)th rotation of the drum,

FIGS. 20(a), 20(b), 20(c), 20(d), 20(e), and 20(f) are diagrams usefulin explaining the direction of the “thin-out exposure process” accordingto the invention,

FIGS. 21(a) and 21(b) are tables showing a spot array of laser light ina conventional “sub-scan direction thin-out exposure” type of theinterlace recording technique,

FIGS. 22(a) and 22(b) are tables showing a spot array of laser light ina conventional “main scan direction thin-out exposure” type of theinterlace recording technique,

FIGS. 23(a), 23(b), and 23(c) are diagrams showing a first exposureoperation in a “thin-out exposure process” according to the sixthembodiment of the invention,

FIGS. 24(a), 24(b), and 24(c) are diagrams showing a second exposureoperation in the “thin-out exposure process” according to the sixthembodiment of the invention,

FIGS. 25(a), 25(b), 25(c), 25(d), 25(e), and 25(f) are diagrams forexplaining the thinning-out direction in the second embodiment of theinvention,

FIG. 26 is a block diagram showing a process in which an image signalcoming from a computer is processed and an image signal to be applied tothe recording head is generated,

FIGS. 27(a), 27(b), and 27(c) are diagrams showing image data of theblocks in FIG. 26.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of a recording method and recording apparatusaccording to the present invention will be described with reference tothe accompanying drawings.

FIG. 1 is a diagram schematically showing a recording apparatusconstructed according to the present invention; FIG. 2 is an enlarged,perspective view showing a recording section of the recording apparatus;FIG. 3 is a cross sectional view showing a structure including an imagereceiving sheet and a transfer sheet, which is used in the recordingmethod and the recording apparatus of the invention; FIG. 4 is a diagramfor conceptually showing a recording process; FIG. 5 is a diagram usefulin explaining the main scan direction. sub-scan direction, laser spotnumbers, line numbers in the sub-scan direction in the recordingapparatus, those items being used for an island pattern exposure of theinvention; and

FIGS. 6 through 11 are explanatory diagrams for explaining an “islandpattern exposure process” of the invention, which is carried out byusing the laser light spots emitted from a recording head.

A recording apparatus 1, as shown in FIG. 1, includes an image receivingsheet supply section 100, a transfer sheet supply section 200, arecording section 300 and a discharge section 400. The recordingapparatus 1 is covered with a body cover 510 and is supported by legparts 520.

In the recording apparatus 1, the image receiving sheet supply section100 supplies an image receiving sheet to the recording section 300. Thetransfer sheet supply section 200 is capable of supplying plural kindsof transfer sheets and selectively supplies one of those transfer sheetsto the recording section 300. In the recording section 300, anothertransfer sheet is wound on the image receiving sheet, which is woundaround a drum 310 as a recording medium fixing member. In this state,laser exposure is carried out in accordance with image information of animage to be recorded onto the recording medium formed by superimposingthe transfer sheet on the image receiving sheet. An image is formed onthe image receiving sheet in a manner that toner on a portion of thetransfer sheet which is heated by the laser exposure process, istransferred and attached to the image receiving sheet by its adhesiondeterioration, fusion or sublimation. Further, toners of differentcolors (e.g., black, cyan, magenta and yellow) on the transfer sheetsare attach to the same image receiving sheet, to thereby forming a colorimage on the receiving sheet. As will be described later, this isrealized in such a manner that the exposed transfer sheets aresuccessively exchanged with transfer sheets of other colors, andsubjected to the laser exposure process.

The image receiving sheet on which the image is formed, is dischargedthrough the discharge section 400 and is taken out from the recordingapparatus. Subsequently, in an image transfer section which isadditionally provided and is not shown, the image receiving sheet isheated and pressed in a state that the image forming surface of theimage receiving sheet is placed on a paper sheet to be printed. By sodoing, the toner is transferred onto the desired paper sheet (printingsheet), whereby the image is formed.

The outline of the recording apparatus 1 is as mentioned above.

For the recording material, reference is made to Japanese patentlaid-open No. 296594/1992, No. 327982/1992 and No. 327983/1992. For thedevice using the above recording material, reference is made to Japanesepatent laid-open No. 290731/1995. For the citation of the recordingapparatus using the embodiment, reference is made to Japanese patentlaid-open No. 277831/1999.

The image receiving sheet supply section 100, the transfer sheet supplysection 200, the recording section 300 and the discharge section 400will be described successively.

The image receiving sheet supply section 100 includes an image receivingsheet roll 130. The image receiving sheet roll 130 is formed by windingthe image receiving sheet 140 around the core. The image receiving sheet140, as shown in FIG. 3, includes a supporting layer 140 a, a cushionlayer 140 b and an image receiving layer 140 c. The cushion layer 140 band the cushion layer 140 b are successively laminated on the supportinglayer 140 a. PET (polyethylene) base, TAC (triacetyl-cellulose) base,PEN (polyethylene naphthalate) base or the like may be used for thesupporting layer 140 a. The image receiving layer 140 c receives thetoner to be transferred. The cushions layer 140 b functions to absorbsteps formed when a plurality of different toner layers are layered onupon the other. In the image receiving sheet roll 130, the imagereceiving layer 140 c is wound so that the image receiving layer 140 cis located outside with respect to the supporting layer 140 a (the imagereceiving sheet roll thus wound will be referred to as an “outerwinding” image receiving sheet roll). The image receiving sheet roll 130is disposed so that it rotates about the central axis of the core.

The image receiving sheet supply section 100 further includes an imagereceiving sheet transporting part 150. The image receiving sheettransporting part 150 includes a motor (not shown), a drive forcetransmitting belt or a chain (not shown), transporting rollers 154 and155, a supporting guide 156, an image receiving sheet cutting part 160and a detection sensor (not shown) for detecting an end point of theimage receiving sheet.

Each of transporting rollers 154 and 155 consists of a couple ofrollers. With this driving mechanism, the image receiving sheet 140 istransported to the recording section 300, and is returned from therecording section 300.

To start, in a state that the leading end of the image receiving sheetroll 130 is nipped between the paired transporting rollers 154, theimage receiving sheet 140 is pulled out by the driving mechanismincluding the motor. With this, the image receiving sheet roll 130rotates, and the image receiving sheet 140 is successively transported.The image receiving sheet 140 thus transported is further transported,while being nipped between the transporting rollers 155 and guided bythe supporting guide 156.

The image receiving sheet 140 thus transported by the image receivingsheet transporting part 150 is cut by the image receiving sheet cuttingpart 160 to have a predetermined length. The detection sensor is usedfor measuring the length of the image receiving sheet. The lengthmeasurement is conducted in a manner that the leading end of the imagereceiving sheet 140 is detected by the detection sensor, and the numberof revolution of the motor is allowed for. The image receiving sheet 140is cut to have a predetermined length on the basis of the measuringresult, and then the sheet thus cut is supplied to the recording section300. The image receiving sheet cutting part 160 includes a cutter, asupporting part and a guide (which are not shown). The image receivingsheet 140 delivered from the image receiving sheet roll 130 by thedriving mechanism, is stopped in its transportation on the basis of theresult of measuring the image receiving sheet, and is cut by the cutterto have a predetermined length.

In this way, the image receiving sheet supply section 100 delivers andcuts a part of the image receiving sheet roll 130, whereby the imagereceiving sheet 140 of a predetermined length is supplied to therecording section 300.

The transfer sheet supply section 200 will be described.

The transfer sheet supply section 200 includes a rotary rack 210. Therotary rack 210 is rotated about a rotary shaft 213, as will bedescribed later. A plurality of transfer sheet rolls 230 (six in thefigure) are installed in the rotary rack 210, and those are radiallyarranged about the rotary shaft 213.

Each of the transfer sheet rolls 230 includes a core, a transfer sheet240 wound around the core, and flanges (not shown) inserted into bothsides of the core. The transfer sheet roll 230 is rotatably supportedabout the core. The outside diameter of the flange is larger than thatof the transfer sheet wound around the core, so that the rolled transfersheet will not be deformed.

Each of the transfer sheet 240, as shown in FIG. 3, includes asupporting layer 240 a, an optical-to-thermal transducing layer 240 band a toner layer 240 c. The optical-to-thermal transducing layer 240 band the toner layer 240 c are successively laminated on the supportinglayer 240 a. A material of the supporting layer 240 a may be selectedfrom among general supporting member materials (e.g., the same materialas that of the supporting layer 140 a as mentioned above), if it allowsthe laser light to transmit therethrough. The optical-to-thermaltransducing layer 240 b functions to transduce laser energy to heat. Amaterial of the optical-to-thermal transducing layer 240 b may beselected from among general optical-to-thermal transducing materials ifthose materials are capable of transducing optical energy to thermalenergy. Examples of those materials are carbon, black substance,infrared absorption dyestuff and a specific wavelength absorbingmaterial. Toner sheets of black (K), cyan (C), magenta (M) and yellow(Y) are used for the toner layer 240 c.

In the transfer sheet roll 230, the toner layer 240 c is wound so thatthe toner layer 240 c is located outside with respect to the supportinglayer 240 a (the transfer sheet roll thus wound will be referred to asan “outer winding” transfer sheet roll). As will be described later, thetoner layer 240 c containing toner ink is transferred to the imagereceiving sheet by laser exposure.

In FIG. 1, there is illustrated a case where the six transfer sheetsrolls 230 are installed within the rotary rack 210. Those six transfersheets may be six kinds of transfer sheets, for example, transfer sheetsof four colors, black, cyan, magenta and yellow, and the transfer sheetsof two special colors (e.g., gold and silver).

The rotary rack 210 further includes transfer sheet deliveringmechanisms 250 corresponding to those transfer sheet rolls 230. Each ofthe transfer sheet delivering mechanisms 250 includes a pair of feedrollers 254 and a supporting guide 256. In the figure, the rotary rackis provided with six transfer sheet delivering mechanisms 250. The feedrollers 254 includes a roller 254 a and a roller 254 b. The roller 254 ais connected to a motor through a gear mechanism and is driven by themotor, as will be described later. The roller 254 a cooperates with theroller 254 b to nip the transfer sheet 240 therebetween at apredetermined pressing force. The roller 254 b rotates in a directionopposite to that of the roller 254 a, and transports the transfer sheet240. The transfer sheet 240 is nipped between the rollers 254 a and 254b, and is moved forward or backward. As the transfer sheet 240 istransported, the transfer sheet roll 230 rotates.

The transfer sheet 240 is supplied to the recording section 300 by thetransfer sheet delivering mechanism 250 thus constructed. In a statethat the leading end of the transfer sheet 240 is caught between thepaired feed rollers 254, the feed rollers 254 are driven by the drivingmechanism such as the motor. By the driving, the transfer sheet 240 isdelivered. Further, the transfer sheet 240 is cut to have apredetermined length at a transfer sheet transporting part 270 to bedescribed later, and is supplied to the recording section 300.

As described above, the rotary rack 210 containing a plurality of thetransfer sheet rolls 230 is capable of selectively supplying the desiredtransfer sheet 240 to the transfer sheet transporting part 270.

The transfer sheet supply section 200 further includes the transfersheet transporting part 270. The transfer sheet transporting part 270includes a motor (not shown), a belt or chain (not shown) fortransmitting a drive force, transporting rollers 274 and 275, a guide276, a transfer sheet cutting part 280 and a detection sensor (notshown) for detecting an end of the transfer sheet. Each of thetransporting rollers 274 and 275 consists of a pair of rollers. Thetransporting rollers 274 and 275 are connected to the motor by way ofthe belt or chain for transmitting the drive force, and driven by themotor to thereby transport the transfer sheet 240.

The transfer sheet 240 may be delivered to the recording section 300 ormoved backward by the driving mechanism thus constructed. The transfersheet 240 thus delivered is cut to have a predetermined length by thetransfer sheet cutting part 280. The detection sensor is used formeasuring the length of the transfer sheet 240. The length measurementmay be conducted in a manner that the end of the transfer sheet 240 isdetected by the detection sensor, and the number of revolution of themotor is allowed for. The transfer sheet 240 is cut to have apredetermined length on the basis of the measuring result, and then thesheet thus cut is supplied to the recording section 300. The transfersheet cutting part 280 includes a cutter, a supporting part, a guide andthe like (which are not shown).

In this way, the transfer sheet supply section 200 delivers and cuts apart of the transfer sheet roll 230, whereby the transfer sheet 240 of apredetermined length is supplied to the recording section 300.

When the transfer sheet 240 is consumed, it is necessary to detach theused transfer sheet roll 230 from the related part and to replace itwith a new transfer sheet 240.

The replacement work of the transfer sheet roll 230 may be carried outin a state that a lid 511 is opened. To carry out the replacement work,the rotary rack 210 is turned, and the transfer sheet roll 230 to bereplaced is moved to a predetermined replacement position correspondingto the lid 511. The replacement work for the image receiving sheet roll130 is also performed after the lid 511 is opened.

The recording section 300 will be described.

The recording section 300 includes the drum 310. The drum 310, as shownin FIG. 2, is hollow and cylindrical in shape, and is rotatablysupported by a frame 320. In the recording apparatus 1, the rotarydirection of the drum 310 is coincident with the main scan direction.The drum 310 is coupled to a rotary shaft of a motor and is driven torotate by the motor. A plurality of holes are formed in the surface ofthe drum 310. The holes are communicatively coupled to a suction devicesuch as a blower or a vacuum pump (not shown).

The image receiving sheet 140 and the transfer sheet 240 are put on thedrum 310, and when the suction device is operated, those sheets areattracted and stuck onto the drum 310.

The drum 310 has a plurality of grooves (not shown), and those grooves,and those grooves are arrayed in a straight line and parallel to therotary shaft of the drum 310. Above the drum 310, a plurality ofpeeling-off pawls (not shown) are arrayed in a straight line andparallel to the rotary shaft of the drum 310.

The recording section 300 includes a recording head 350. The recordinghead 350 is capable of emitting a laser light Lb. Toner ink at aposition on the transfer sheet 240, which is irradiated with the laserlight Lb, is transferred onto the surface of the image receiving sheet140. The recording head 350 is linearly moved by a driving mechanism(not shown) along a guide rail 322 in a direction parallel to the rotaryshaft of the drum 310. In the recording apparatus 1, the movingdirection of the recording head is coincident with the sub-scandirection. When the rotating motion of the drum 310 and the linermovement of the recording head 350 are combined, the recording head isable to irradiate, for exposure, a desired position on the transfersheet 240 covering the image receiving sheet 140 with laser lightemitted therefrom. Accordingly, a desired image may be transferred tothe image receiving sheet 140 in a manner that the surface of thetransfer sheet 240 is scanned with the image-depicting laser light Lb,and only the positions on the sheet as defined by image information areexposed to the laser light.

The laser light Lb emitted from the recording head 350 will be describedin detail.

The recording head 350 includes a light emitting element (not shown) foremitting the laser light Lb or includes an optical modulating elementfor modulating the laser light emitted from the light emitting element.Laser light spots may be arrayed as desired in a manner that a pluralityof light emitting elements are arrayed at desired positions, and amodulation windows are arrayed at desired positions.

In the embodiment, the laser light emitted from the recording head 350is used for executing an “island pattern exposure process” of theinvention (FIGS. 6 through 11). This will be described later in detailafter the remaining portions of the recording apparatus of the inventionare described.

The operation of winding the image receiving sheet 140 and the transfersheet 240 onto the drum 310 will be described.

The two kinds of sheets, the image receiving sheet 140 and the transfersheet 240, are wound around the drum 310. To start, the image receivingsheet 140 supplied from the image receiving sheet supply section 100 iswound on the drum 310. As described above, a plurality of holes (notshown) are formed in the surface of the drum 310, and the imagereceiving sheet 140 is attracted thereto by the suction device (notshown). With this, the image receiving sheet 140 is wound around thedrum 310 with the rotation of the drum 310, while being attracted to thedrum 310.

Subsequently, a single transfer sheet 240 supplied from the transfersheet supply section 200 is wound on the image receiving sheet 140. Thetwo kinds of sheets, the image receiving sheet 140 and the transfersheet 240, are different in size. The transfer sheet 240 is larger thanthe image receiving sheet 140 in the longitudinal and lateraldirections. Therefore, the transfer sheet 240 is attracted to the drum310 by its portion exceeding the image receiving sheet 140. Withrotation of the drum 310, the transfer sheet 240 is wound while beingattracted to the drum 310.

When the image receiving sheet 140 and the transfer sheet 240 are woundon the drum 310, the toner layer 240 c of the transfer sheet 240 is incontact with the image receiving layer 140 c of the image receivingsheet 140. Toner ink on the toner layer 240 c thus positionally relatedis exposed to the laser light by the recording head 350, as describedabove, and is transferred to the image receiving sheet 140. The transfersheet 240 having undergone the transferring operation is peeled off fromthe drum 310.

Next, the peeling-off process will be described.

To start, the drum 310 is rotated to a predetermined position at whichthe transfer sheet is peeled off. The tip of each peeling-off pawl ismoved from a standby position at which the pawls are not in contact withthe drum 310, to a position at which the pawls come in contact with thedrum 310. At the time of moving of the pawls, the tip of eachpeeling-off pawl is kept away from the transfer sheet 240. With therotation of the drum 310, the peeling-off pawls relatively move on thedrum 310 and along the surface of the drum 310 in the circumferentialdirection. The tip of each peeling-off pawl relatively moves along thegroove formed therein on the surface of the drum 310, and advances tounder the transfer sheet 240. At this time, the transfer sheet 240 movesalong the upper surface of the peeling-off pawls, and then the transfersheet 240 is peeled off from the drum 310.

The peeling-off pawls rise in a direction in which the pawls move apartfrom the drum 310 before those come contact with the image receivingsheet 140, and move to the standby position. After the leading end ofthe transfer sheet 240 is peeled off, the transfer sheet 240 is furtherpeeled off from the drum 310 and the image receiving sheet 140, with therotation of the drum 310. At this time, the image receiving sheet 140remains attracted to the drum 310 by the sucking force of the suckingdevice, and accordingly, only the transfer sheet 240 may be peeled off.

The transfer sheet 240 thus separated, is discharged outside theapparatus by way of the discharge section 400 to be described later.

Subsequently, a transfer sheet 240 of another color is wound, by theabove procedure, on the image receiving sheet 140 remaining wound on thedrum 310. After the above-mentioned operation is performed, and thetoner ink of the transfer sheet 240 is transferred on the imagereceiving sheet 140 by the laser exposure process, the transfer sheet240 is peeled off and discharged.

A similar same operation is repeated for given plural kinds of transfersheets 240. The operation is repeated for four kinds of transfer sheets240 of, for example, black, cyan, magenta and yellow, so that a colorimage is transferred on the image receiving sheet 140.

Finally, the image receiving sheet 140 having the plural kinds of tonerinks thus transferred thereon is peeled off. The image receiving sheet140 is peeled off in a similar way to that of peeling off the transfersheet 240. At this time, the peeling-off pawls approach plural groovesand separate the image receiving sheet 140 from the drum 310. The samepeeling-off pawls as used when the transfer sheet 240 is peeled off maybe used, so that the mechanical structure thereof may be simplified.Accordingly, the apparatus reliability is improved.

The image receiving sheet 140 thus separated is discharged to thedischarge section 400.

The discharge section 400 will be described.

The discharge section 400 includes a sheet common transporting part 410,a transfer sheet discharge part 440 and an image receiving sheetdischarge part 450.

The sheet common transporting part 410 includes a motor (not shown), abelt or chain (not shown) for transmitting drive force, transportingrollers 414, 415 and 416, supporting guides 418 and 419, and a detectionsensor (not shown). The sheet common transporting part 410 furtherincludes a movable guide part made up of a guide plate 438 and a drivingmechanism (not shown). The guide plate 438 is movable between twopositions to be described later when it is driven by the drivingmechanism.

The transfer sheet discharge part 440 is used for discharging theprocessed transfer sheet 240 to a transfer sheet recovering box 540.

The image receiving sheet discharge part 450 includes an image receivingsheet exit port 451, rollers 454 and 455, and a guide 458. The imagereceiving sheet 140 having an image transferred thereto is discharged toa tray 550, through the image receiving sheet discharge part 450.

Each of transporting rollers 414, 415, 416, 454 and 455 consists of apair of rollers, like as other transporting rollers already stated. Thepaired rollers nip the image receiving sheet 140 and the transfer sheet240, and in this state, transport those sheets.

The discharge section 400 having such a mechanism discharges the imagereceiving sheet 140 and the transfer sheet 240 in the following manners.

The discharging of the transfer sheet 240 will first be described.

The transfer sheet 240, which has been laser exposed in the recordingsection 300 and been out of use, is peeled off from the drum 310 by theabove procedures. The transfer sheet 240 separated is transportedforward, while being supported by the peeling-off pawls, the supportingguides 418 and 419, and the guide plate 438, and being nipped betweenthe transporting roller pairs 414, 415 and 416.

Next, the discharging of the image receiving sheet 140 will bedescribed.

After the image receiving sheet 140 receives the toner ink and isprocessed in the recording section 300, it is peeled off from the drum310, as mentioned above. The separated image receiving sheet 140 istransported forward, while being supported by the peeling-off pawls, thesupporting guides 418 and 419, and the guide plate 438, and being nippedbetween the transporting roller pairs 414, 415 and 416.

The sheet common transporting part 410 is also used for the dischargingof the transfer sheet 240. Therefore, the sheet transport mechanism issimpler than in the case where the transport parts are respectivelyprovided for those sheets. In the sheet common transporting part 410,the transfer sheet 240 is transported in a state that the toner layerthereof is directed downwards. The image receiving sheet 140 istransported in a state that the image receiving layer thereof isdirected upwards. Therefore, when the image receiving sheet 140 and thetransfer sheet 240 are successively transported by utilizing the sametransporting path, there is no fear that the image formed on the imagereceiving layer of the image receiving sheet 140 is soiled.

The image receiving sheet 140 is transported by the transporting rollers414, 415 and 416, and is temporarily discharged outside the apparatus.In this case, however, the whole image receiving sheet 140 is dischargedoutside. To be more specific, in a state that the trailing end of theimage receiving sheet 140 is put on the guide plate 438 and is nippedbetween the transporting roller pair 416, the driving by the motor istemporarily stopped, and the motor is reversely turned to move the imagereceiving sheet 140 back to the image receiving sheet exit port 451.That is, the “switch-back” operation is performed. A timing of stoppingthe driving by the motor is determined by using a signal derived fromthe detection sensor. The detection sensor detects that the trailing endof the image receiving sheet 140 passes the position of the detectionsensor. Then, the image receiving sheet 140 is transported and reaches apredetermined position, and at this time, the driving by the motor isstopped.

Here, the “predetermined position” means a position at which thetrailing end of the image receiving sheet 140 is put on the guide plate438 and is nipped between the transporting roller pair 416. Whether ornot the image receiving sheet 140 is moved a predetermined distance tillit reaches this position, is judged from, for example, the number ofpulses representative of a rotation of the motor, which is counted froman instant that the detection sensor detects the trailing end of theimage receiving sheet.

The guide plate 438 of the movable guide part is driven by a drivingmechanism (not shown) and is movable between a position indicated by asolid line and another position by a broken line. Thus, the guide plate438 is moved by the driving mechanism. When the motor being standstillis reversely rotated, the transporting rollers 416, 454 and 455 aredriven in the reverse direction. By the reverse rotation, the imagereceiving sheet 140 is moved backward. The image receiving sheet 140 isfurther transported, by the transporting rollers 454 and 455, to thetray 550, while being supported by the guide 458. The image receivingsheet having been delivered to the tray 550 is taken out from therecording apparatus, as described above, and is additionally processedat an image transfer section, which is separately provided. As a result,the image is printed on a desired printing sheet.

The operation described above is controlled by a controller section (notshown).

The controller section controls the image receiving sheet supply section100, the transfer sheet supply section 200, the recording section 300,the discharge section 400 and the like. In the respective sections, thecontroller section controls the driving part including the motor and thelike. Particularly, in the recording section 300, the controller sectionfurther controls the air part, such as the suction device, and an imageprocessing part for processing image data. The driving part of thetransfer sheet supply section 200 includes two driving systems, i.e., arotation driving system for the rotary rack 210 and a sheet-transportdriving system for supplying the transfer sheet 240 from the transfersheet roll 230 to the drum 310. For the driving of the motor in thesheet-transport driving system drives the motor, the driver for motordriving is used commonly for the plurality of transfer sheet deliveringmechanisms, as described above. Accordingly, the drive circuit system issimplified.

The recording apparatus as described above is capable of forming adesired color image on the image receiving sheet 140.

Description will be given on operation procedures when a color image isformed by using four colors, black, cyan, magenta and yellow.

To start with, as shown in FIG. 4, in a step 1, the image receivingsheet supply section 100 supplies an image receiving sheet 140 to thedrum 310. In this case, the image receiving sheet 140 is supplied in amanner that a part of the outer-winding image receiving sheet roll 130is delivered and cut, and is wound on the drum 310.

In a step 2, the transfer sheet supply section 200 supplies a transfersheet 240 of black (K) to the drum 310.

Specifically, the rotary rack 210 of the transfer sheet supply section200 rotates to thereby move the transfer sheet roll 230 of black to aposition facing the transfer sheet transporting part 270. The transfersheet 240 is supplied in a manner that a part of the outer-windingtransfer sheet roll 230 is delivered and cut, and is wound on the drum310. At this time, the leading end of the transfer sheet 240 beingdelivered from the transfer sheet roll 230 is at a position near thecutter 280 disposed outside the rotary rack 210. In this case, followingthe supply of the transfer sheet 240, the transfer sheet deliveringmechanism 250 reversely turns the feed roller 254 to store the leadingend of the transfer sheet roll 230 on the inner side of the outerperipheral of the rotary rack 210. Also in this case, the feed rollers254 still nip the leading end of the transfer sheet roll.

In a step 3, the transfer sheet 240 is heated and pressed, andlaminated. This laminating process is omitted sometimes.

In a step 4, a latent image is formed on the image receiving sheet 140in accordance with image data previously applied. The image data isfurther color separated into image data of respective colors. Laserexposure is performed in accordance with the color separated image dataof the respective colors. The recording head 350 irradiates the transfersheet 240 with image forming laser light spots Lb in accordance with thecolor image data after color separated. Toner ink of the transfer sheet240 is transferred onto the image receiving sheet 140, and an image isformed on the image receiving sheet 140.

In a step 5, only the transfer sheet 240 of “K” is peeled off from thedrum 310. The transfer sheet 240 having been separated from the drum 310is discharged through the discharge section 400 to the transfer sheetrecovering box 540.

At this time, judgement is made as to whether or not the transferoperation has been performed for the transfer sheets 240 of all colors.If the supply of another kind of transfer sheet 240 is needed, thesequence of operations from the steps 2 to 5 is repeated. In otherwords, the sequence of operations steps 6 to 17 is repeated for thetransfer sheets 240 of other colors, cyan, magenta and yellow. As aresult, the toner inks of K, C, M and Y of four-color transfer sheetsare transferred to one image receiving sheet 140, so that a color imageis formed on the image receiving sheet 140.

When the process ends, it is judged that the laser exposure of the finaltransfer sheet 240 is completed.

And, the image receiving sheet 140 is peeled off from the drum 310. Thepeeled image receiving sheet 140 is discharged through the dischargesection 400 to the tray 550, while undergoing the switch-back operation.In the image transfer part separately provided, the toner ink is furthertransferred from The image receiving sheet 140 as discharged onto adesired printing sheet. By this, the color printing for color proofingis performed.

The “island pattern exposure process” of the invention will be describedby taking a called “solid recording” as an example. FIG. 5 is a diagramfor explaining the main scan direction, sub-scan direction, laser spotnumbers, line numbers in the sub-scan direction in the recordingapparatus, which are used for the island pattern exposure process of theinvention.

In the figure, the main scan direction of the recording apparatus iscoincident with the rotational direction of the drum, and in the figure,the drum rotates in the upward direction as indicated by an arrow.Accordingly, a relative motion of the laser spot takes a downwarddirection as indicated by an arrow in the figure. The sub-scan directionis coincident with the moving direction of the recording head, and therecording head moves from left to right as indicated by an arrow in thefigure. 24 number of laser spots to be formed on the recording medium bya laser beam emitted from the recording head are substantiallyhorizontally arrayed, and those spots are numbered 1 to 24 in the orderfrom the end of the sub-scan. In this instance, the number of laserspots is set at 24. Such number is selectively used for ease ofexplanation, but actually, 32 to 2000 number of laser spots are used. Adistance between the center of one laser spot to the center of anotherlaser spot adjacent to the former may be set within a range from 1 μm to30 μm. Description will be given using a case where the center-to-centerdistance is about 10 μm.

Numerals “1s” are printed at positions under the line numbers 1 to 24arranged in the sub-scan direction, respectively. Of those line Nos. 1to 24, the line No. 1 does not indicate a start position of thesub-scanning operation, but it indicates a desired sub-scanning positionduring the course of exposure operation, as a generalization. The linesare numbered 1 to 24, 25, 26, . . . from the upstream position as viewedin the sub-scan direction. In the description, the sub-scan line No. 1is aligned with the spot No. n (24).

FIGS. 6 and 7 show an “island pattern exposure process” according to thefirst embodiment. A first exposure operation is performed while formingisland patterns, by moving the recording head to a position near the endof the sub-scan (FIGS. 6(a) and 6(b)). Then, the recording head isreturned to a position near the original position of the sub-scan, andan exposure operation is performed again, while forming invertedpatterns (FIGS. 7(a) and 7(b)).

(1) FIG. 6(a) shows an exposure state on the recorded recording mediumfixed to the drum at the m-th rotation of the drum. A letter S indicatesan island pattern configured according to the invention. This islandpattern S consists of an aggregation of “black squares” indicative ofexposed pixels recorded at the m-th rotation of the drum.

Other white squares other than the island patterns S are unexposedpixels. Specifically, at the m-th rotation of the drum in the firstexposure operation, an area defined by the lines Nos. 1 to 24 arrayed inthe sub-scan direction (area A) are exposed by using the spots Nos. 1 to24, to thereby form an array of island patterns as of the “blacksquares” of FIG. 6(a) in the figure.

(2) Then, at the (m+1)th rotation of the drum in the first exposureoperation, an area defined by the lines Nos. 25 to 48 (area B) arrayedin the sub-scan direction are exposed by using the spots 1 to 24, tothereby form an array of island patterns as of the “black squares” ofFIG. 6(a). An array of the island patterns is similar to that of theisland patterns of the “black square” of FIG. 6(b) in the figure.

(3) Subsequently, the recording head is successively moved to the lineNo. 49 and the subsequent ones, while repeating the sequence of exposureoperations mentioned above.

The recording head is moved to a position near the end position of thesub-san, and the first exposure operation in the sub-scan directionends.

(4) After the first exposure operation (sub-scanning operation of therecording head) ends, the recording head is returned to the originalpoint of the sub-scan, and the recording by the second exposureoperation is performed as shown in FIGS. 7(a) and 7(b).

In FIG. 7(a), the unexposed portion, which is thinned out in the firstisland pattern exposure, in the area defined by the lines Nos. 1 to 24(area A) arrayed in the sub-scan direction are exposed as indicated by“dot” marks by using the spots Nos. 1 to 24.

(5) At the (m+1)th rotation of the drum in the second exposureoperation, as in FIG. 7(b), an area defined by the lines Nos. 25 to 48arrayed in the sub-scan direction (area B) are exposed as indicated by“dot” marks by using the spots Nos. 1 to 24.

Thus, when the exposed part by the first exposure operation and theexposed part by the second exposure operation are combined, a solidrecording is formed. Further, the laser energy is not concentrated tothe sub-scan lines No. 1 to 24 at a dash, unlike in the conventionaltechnique, but the same lines arrayed in the sub-scan direction areexposed by plural exposure operations (two exposure operations in thisinstance). Accordingly, the load by the heat of the recording medium issmall, and an amount of gas generated through one main scan is small.

In the first instance of the first embodiment, after the first exposureoperation ends, the recording head is returned to a position near theoriginal point in the sub-scan direction. In alternative, the recordinghead peforms the second exposure operation, while the recording headreturns from the end point of the sub-scan direction to near theoriginal point. The alternative gains the time taken till it returns tothe original point to thereby lead to improvement of the productivity.

In the description thus far made, the “island pattern exposure process”is executed by two exposure operations, viz., the “island patternexposure process” is executed by repeating the exposure operation twotimes, or the exposure operation for the “island pattern exposureprocess” is divided into two operations. However, it will readily beunderstood that the number of divisions of the exposure operation forthe “island pattern exposure process” is not limited to 2, but may be 3or R, larger 3. As the number R of divisions is increased, theproductivity becomes low, but the resultant image recorded is clear withlessened image defects.

In this case, at the first exposure, a percentage of the island patternsof the whole image/character data to be exposed is preferably 20% to80%.

At the R-th exposure, a percentage of the image/character data otherthan those exposed in the first to (R−1)th exposure operations to thewhole image character data to be exposed is preferably 20% or higher.

FIGS. 8(a), 8(b), and 8(c) are diagrams showing a second instance of thefirst embodiment in which the “island pattern exposure process” isexecuted by only one exposure operation. In the second instance, all thespots Nos. 1 to 24 by the recording head shown in FIG. 5 are dividedinto two blocks, a first block consisting of the spots Nos. 1 to 12, anda second block of the spots Nos. 13 to 24. The recording head is movedfrom the original point of the sub-scan to a position of the endthereof, while executing the “island pattern exposure process” by usingthe first block of spots, and executing the inversion exposure of theunexposed pixels other than the island patterns by using the secondblock of spots. In this case, it is preferable that the spots areequally divided into two blocks.

(1) In FIG. 8(a) showing an exposure state on the recorded recordingmedium at the m-th rotation of the drum, an area defined by the linesNos. 1 to 12 (area A) arranged in the sub-scan direction is subjected tothe “island pattern exposure process” which is carried out by using thefirst block (consisting of the spots Nos. 1 to 24 in FIG. 5) to therebyrecord a pattern of “black squares” in the figure on the recordingmedium.

(2) Subsequently, at the (M+1)th rotation of the drum, the recordingmedium is exposed to have a pattern of black parts in FIG. 8(b).Specifically, an area defined by the lines Nos. 13 to 24 on therecording medium (area B) are subjected to the “island pattern exposureprocess” which is carried out by using the first block (spots Nos. 1 to12). The remaining portion (unexposed area) of the area defined by thelines Nos. 1 to 12 on the recording medium is subjected to the inversionexposure which is carried out by using the second block (spots Nos. 13to 24).

Accordingly, as the result of the exposure operations at the m-throtation and the (M+1)th rotation of the drum, a solid recording of thearea defined by the lines Nos. 1 to 12 on the recording medium asindicated in FIG. 8(c), is completed.

Thus, the recording medium is exposed two times; a first exposureoperation is executed for the area containing the island patterns on therecording medium and the other exposure operation is for the remainingarea. Further, the laser energy is not concentrated, at a dash, to thesub-scan lines No. 1 to 24 arrayed in the sub-scan direction.Accordingly, the load by the heat of the recording medium is small, andan amount of gas generated through one main scanning operation is small.

In the description thus far made, the spots of the recording head isdivided into two groups of spots; however, those may be divided into “n”(n=3 or larger) number of groups of spots. As the number “n” ofdivisions is increased, the productivity becomes low, but the resultantimage recording is clear with lessened image defects.

In this case, a percentage of the island patterns, which are formed bythe exposure using the first block, to the whole image character data tobe exposed is preferably 20% to 80%.

At the exposure by the n-th block, a percentage of the image characterdata other than those exposed in the first to (n−1)th exposureoperations to the whole image character data to be exposed is preferably20% or higher.

FIGS. 9(a), 9(b), 9(c), and 9(d) are diagrams for explaining a shape ofan island pattern not having gas stagnation, which is a secondembodiment of the invention.

At a recording local area of the recording medium, which is irradiatedwith the laser spots, optical energy of the laser light isinstantaneously converted into thermal energy by the optical-to-thermaltransducing layer. And water and organic solvent, which are contained inthe optical-to-thermal transducing layer and the toner layer, arevolatilized, and called gas is generated. Therefore, in the recordingmethod in which the image receiving sheet and the transfer sheet areplaced one on the other, and an acting layer acting in connection withthe laser light is placed between those sheets, the gas generated ishard to run out into the air, and stays between the image receivingsheet and the transfer sheet. The island pattern of the secondembodiment is configured so as not to have gas stagnation.

An island pattern shown in FIGS. 9(a), (9(b), 9(c), and 9(d) has aninappropriate shape in which gas is easy to stagnate. An island patterncontains a recessed part T which is not exposed in the precedingexposure operation by the first block, on its downstream side as viewedin the main scan direction. This part is a part at which gas willpossibly stagnate. This will be described with reference to FIGS. 9(a),9(b), 9(c), and 9(d). All the spots of the recording head are dividedinto two blocks of spots. The “island pattern exposure process” isexecuted by using the first block of spots. The unexposed pixels otherthan the island patterns are subjected to the inversion exposure whichis carried out by using the second block of spots. FIG. 9(a) shows anexposure state on the recording medium when an “island pattern exposureprocess” of an area defined by the lines Nos. 1 to 12 arrayed in thesub-scan direction, which is carried out by using the first block (spotsNos. 13 to 24) at the m-th rotation of the drum, is completed. It isassumed that gas is generated at an areal part including the lines Nos.4 and 5, and the ninth row.

FIG. 9(b) shows an exposure state on the recording medium that theexposure of the sub-scan direction proceeds to a point near the ninthrow at the (m+1) rotation of the drum. In the figure, the lines Nos. 13to 24 arrayed in the sub-scan direction are thinned out by the exposureoperation using the first block (spots Nos. 13 to 24) thereby form anisland pattern. When the unexposed part defined by the lines Nos. 1 to12 arrayed in the sub-scan direction are progressively exposed, gas Gappears in a part near the ninth row. In the exposed part, the imagereceiving sheet and the transfer sheet are in close contact with eachother. Therefore, it is impossible for gas G to stagnate at the exposedpart. As the exposed part moves in the main scan direction, the gas G isdriven to move to the upstream side in the main scan direction.Accordingly, the gas G is driven to move in the direction of an arrow.If the recessed part T, which is not exposed by the preceding exposureoperation by the first block of spots, is present in the arrowdirection, the gas G will enter into the recessed part.

FIG. 9(c) shows a state on the recording medium when the gas G has beendriven to flow into the unexposed recessed part T of the island pattern.

In turn, the gas having been put in the unexposed, recessed part T ofthe island pattern cannot further move forward since an upstream part inthe main scan direction is not exposed. Accordingly, the gas stagnatesat this recessed part.

FIG. 9(d) shows an exposure state on the recording medium after theisland pattern containing the stagnant gas G therein has been exposed inthe main scan direction. The gas trapped in the recessed part T of theisland pattern hinders the close contact between the image receivingsheet and the transfer sheet, possibly causing white voids.

As seen from foregoing description, such a problem arises from the factthat the island pattern shown in FIGS. 6(a) and 6(b) includes theunexposed, recessed part on its downstream side as viewed in the mainscan direction. In other words, the solution to the problem is toeliminate that recessed part. To solve the problem, what a designer hasto do is to configure the island pattern so as to be flat or outcurvedat its downstream side as viewed in the main scan direction.

FIGS. 10(a), 10(b), 10(c), and 10(d) are explanatory diagrams forexplaining an island pattern free from the pattern omission, which formsa third embodiment of the invention.

FIGS. 10(a) and 10(b) show an inappropriate island pattern in which theomission of pattern is easy to occur. FIG. 10(a) shows its islandpattern, and FIG. 10(b) shows the same in an enlarged fashion. FIG.10(c) and 10(d) show an example of the island pattern free from thepattern omission phenomenon, which forms a third embodiment of theinvention. FIG. 10(c) shows its island pattern, and FIG. 10(d) shows thesame in an enlarged fashion.

In FIG. 10(a), as shown in the enlarged view of FIG. 10(b), each islandpattern includes a 1 dot protruded part (X part), which is protrudedfrom each of the four sides of the island pattern by a distance of onedot. It was found that the protruded part causes the pattern omission.The reason for this follows. The area around the three sides of the top,bottom, right and left sides of the one-dot protruded part is theunexposed part and cold. Accordingly, if one dot protruded part isexposed, the resultant heat dissipates in three directions. As a result,the pattern omission phenomenon occurs.

Island patterns shown in FIG. 10(c), as shown in FIG. 10(d) of the samefigure in an enlarged manner, each island pattern includes two-dotprotruded parts (marked with circles) each protruded from its four sidesby a distance of two or more dots, not the one-dot protruded parts. Withprovision of the two-dot protruded parts, there is eliminated thepattern omission. The reason for this is reverse to the reason for thepattern omission previously stated. In this island pattern, the coldarea is the area adjacent to only two sides of the top, bottom, rightand left sides of each two-dot protruded part. Accordingly, therecording local area can be heated to a temperature necessary for imagetransferring.

As seen from the description of the third embodiment, it is preferableto configure the island pattern such that at least two sides of theisland pattern have recording dots.

FIGS. 11 and 12 show diagrams useful in explaining a fourth embodimentof the invention. FIGS. 11(a), 11(b), 11(c), and 11(d) are explanatorydiagrams for explaining an inappropriate island pattern which blocks theflowing of gas generated in the preceding thin-out exposure operation tothe outside of the recording medium. FIGS. 12(a), 12(b), 12(c), and12(d) are diagrams showing a fourth embodiment of the invention, whichdefines island patterns enabling the flowing of gas generated in thepreceding thin-out exposure operation to smoothly flow out of therecording medium.

FIG. 11(a) shows an exposure state of the recording medium when the(M+1)th rotation of the drum ends, and a solid recording in an areadefined by the lines Nos. 1 to 12 arrayed in the sub-scan direction,which is performed by using the second block (spots Nos. 13 to 24), iscompleted, and an “island pattern exposure process” of an area definedby the lines Nos. 13 to 24 arrayed in the sub-scan direction, which isperformed using the first block (spots Nos. 1 to 12), is completed. Itis assumed that at this time, gas indicated by G is generated at a partincluding the lines Nos. 16 to 17, and the rows Nos. 12 to 14.

FIG. 11(b) shows an exposure state on the recording medium that thesolid recording (dotted area) has reached a position near the 11th linein the main scan direction at the (M+2)th rotation of the drum. In thefigure, an area defined by lines Nos. 13 to 24 arrayed in the sub-scandirection is inversion exposed by using the second block (spots Nos. 13to 24), whereby the solid recording is executed. The recording processunder progression encounters the gas G. In the exposed part, the imagerecording sheet and the transfer sheet are in close contact with eachother. Accordingly, the gas G cannot stagnate in the exposed part, andthis part functions to drive the gas G to move in the main scandirection. The island pattern is configured such that as the recordinghead moves in the main scan direction, the gas G is driven to moveupstream in the sub-scan direction (=an arrow direction). Accordingly,the gas G flows to the already exposed area located upstream in thesub-scan direction, as shown in FIG. 11(c). And the gas G is trapped ata recorded part where the exposure is completed as indicated in FIG.11(d), possibly forming a void.

Turning to FIGS. 12(a), 12(b), 12(c), and 12(d), there is shown anisland pattern which allows the gas to move outside the recordingmedium. FIG. 12(a) shows an exposure state on the recording medium thatthe rotation of the (m+1)th rotation of the drum ends, and the solidrecording on an area defined by the lines Nos. 1 to 12 arrayed in thesub-scan is completed by using the second block (spots Nos. 13 to 24),and an “island pattern exposure process” of an area defined by the linesNos. 13 to 24 arrayed in the sub-scan direction, which the process iscarried out using the first block (spots Nos. 1 to 12), is completed. Itis assumed that at this time, gas is generated at an areal partincluding the lines Nos. 16 to 17, and the 12th to 14th rows.

FIG. 12(b) shows an exposure state on the recording medium that thesolid recording proceeds to a point near the 11th row as viewed in thesub-scan direction at the (m+2) rotation of the drum. In the figure, anarea defined by lines Nos. 13 to 24 arrayed in the sub-scan direction isinversion exposed by using the second block (spots Nos. 13 to 24),whereby the solid recording is executed. The recording process underprogression encounters the gas G. In the exposed part, the imagerecording sheet and the transfer sheet are in close contact with eachother. Accordingly, the gas G cannot stagnate in the exposed part, andthis part function to drive the gas G to move upstream as viewed in themain scan direction. The island pattern is configured such that as therecording head moves in the main scan direction, the gas G is driven tomove downstream in the sub-scan direction. Accordingly, the gas G movesto the unexposed part located downstream in the sub-scan directionindicated by an arrow. Accordingly, the gas G moves as shown in FIG.12(c), and further moves to the unexposed part located upstream in themain stream and downstream in the sub-scan direction, and finally it isdischarged from the end of the recording medium to exterior, as shown inFIG. 12(d).

As described above, it is seen from the third embodiment of theinvention that a preferable island pattern is configured to be slantedto the downstream side in the sub-scan direction, and to the upstreamside in the main scan direction.

It is also seen that for the same reason, an array of plural islandpatterns is preferably directed to the downstream side in the sub-scandirection and to the upstream in the main scan direction.

When the island pattern is so configured and the island patterns arearrayed as mentioned above, there is no chance that the gas stagnatesbetween the toner layer 240 c (FIG. 3) and the image receiving layer 140c in the recorded area, the close contact between the toner layer 240 cand the image receiving layer 140 c is maintained, and the image defectarising from the spot array is prevented.

The exposure method effectively operates when the dot area rate is 70%or higher, particularly for the solid part (where the dot area rate is100%).

FIG. 13 is a block diagram showing a process in which an image signalcoming from a computer is processed and an image signal to be applied tothe recording head is generated.

1) An image signal coming from a computer is input to an image signalinput section in the controller section. An image signal from thecomputer takes a form as shown in FIG. 14(a).

2) The image signal input section takes out an image signal of the m-throtation of the drum from the image signal coming from the computer, andsends it to a pattern signal processor section.

3) The pattern signal processor section computes the image signals ofthe first to n-th blocks of the m-th rotation of the drum, and sends itto an image signal output section.

4) The image signal output section drives the recording head forexposure in accordance with the incoming image signals.

FIG. 14(b), 14(c), 14(d), and 14(e) are diagrams showing a process inwhich the image signal as shown in FIG. 14(a) is exposed in a thin-outmanner and recorded according to the invention. FIG. 14(b) shows imagedata of the first block oft the m-th rotation of the drum. As seen, therecording medium is exposed in thin-out patterns, which are slanted tothe downstream side in the sub-scan direction and to the upstream sidein the main scan direction.

FIG. 14(c) shows image data of the first block of the (m+1)th rotationof the drum.

FIG. 14(d) shows image data of the second block produced of the (m+1)throtation of the drum.

As seen, those patterns are slanted to the downstream side in thesub-scan direction and to the upstream side in the main scan direction,and are used for exposing the unexposed area which is thinned out inFIG. 14(b).

FIG. 14(e) show an exposed area defined by the lines Nos. 1 to 12arrayed in the sub-scan direction, which has undergone the exposureoperations of FIGS. 14(b), 14(c) and 14(d). As seen, the image signalcoming from the computer is clearly recorded without any gas stagnation,in the form of the same image as of the area defined by the lines Nos. 1to 12 in FIG. 14(a).

In the embodiments mentioned above, the recording medium fixing memberof the outer drum type is presented by way of example. It may be of theinner drum type in which the recording medium is fixed to the incurvedsurface or the inner peripheral surface of a cylinder, and a laser beamis emitted, for recording, from the center of incurved surface or thecylinder. A recording device of the type in which a laser beam is movedin the main scan direction, and the recording medium is transported inthe sub-scan direction by means of a transporting mechanism, may also beused instead of the drum. The recording medium fixing member may be ofthe flat table type in which it is movable in the main scan direction.While the laser light spots one dimensionally arrayed are used in theembodiments, the laser beam spots two dimensionally arrayed may also beused instead.

As seen from the foregoing description, in the recording method andrecording apparatus of the invention, in the first exposure operation inwhich the recording head is moved from the original point in thesub-scan direction to a position near the end point of the same, theimage/character data is exposed by the “island pattern exposureprocess”. In the first exposure operation and the subsequent ones, thepixels in the unexposed area other than the area island pattern exposureprocessed are successively exposed. Accordingly, the thermal energy isdispersed, and the load by the heat of the recording medium is small.

Gas generated at a local area of the recording medium is successivelymoved to the downstream part in the sub-scan direction and the upstreampart in the main scan direction, and moved to the non-recorded area, andfinally discharged outside the recording medium. As a result, theinvention prevents the gas from stagnating between the toner layer andthe image receiving layer, and succeeds in eliminating the cause of theimage defect.

FIGS. 16(a), 16(b), 16(c), 17(a), 17(b), and 17(c) are diagrams showinga first instance of the fifth embodiment in which the exposure processis executed by only one exposure operation. In the first instance, allthe spots Nos. 1 to 24 by the recording head shown in FIG. 5 are dividedinto two blocks, a first block consisting of the spots Nos. 1 to 12, anda second block of the spots Nos. 13 to 24. The recording head is movedfrom the original point of the sub-scan to a position of the end pointthereof, while executing the “thin-out exposure process” by using thefirst block of spots, and executing the inversion exposure of the pixelsremaining unexposed after the execution of the “thin-out exposureprocess”, by using the second block of spots. In this case, it ispreferable that the spots are equally divided into two blocks.

(1) FIG. 16(a) showing an exposure state on the recorded recordingmedium at the m-th rotation of the drum, an area defined by the linesNos. 1 to 12 arranged in the sub-scan direction is subjected to the“thin-out exposure process” using the first block (consisting of thespots Nos. 13 to 24) to thereby record patterns of “1” on the recordingmedium as shown.

(2) Subsequently, at the (M+1)th rotation of the drum, the recordingmedium is exposed to have patterns of “2” in FIG. 16(b). Specifically,an area defined by the lines Nos. 13 to 24 on the recording medium aresubjected to the “thin-out exposure process” using the first block(spots Nos. 1 to 12). The remaining part (unexposed area) of the areadefined by the lines Nos. 1 to 12 on the recording medium is subjectedto the inversion exposure using the second block (spots Nos. 13 to 24),and a solid recording of this area is completed.

(3) At the (M+2)-th rotation of the drum, the recording medium isexposed to have patterns of “3” in FIG. 16(c). Specifically, an areadefined by the lines Nos. 25 to 36, which are arrayed in the sub-scandirection, on the recording medium is subjected to the “thin-outexposure process” using the first block (spots Nos. 1 to 12). Anunexposed area of the area defined by the lines Nos. 13 to 24, which arearrayed in the sub-scan direction; on the recording medium is exposed tohave patterns of “3”, by the second block (spots Nos. 13 to 24).

(4) At the (M+3)-th rotation of the drum, the recording medium isexposed to have patterns of “4” in FIG. 17(a). Specifically, an areadefined by the lines Nos. 37 to 48, which are in the sub-scan direction,on the recording medium are subjected to the “thin-out exposure process”using the first block (spots Nos. 1 to 12). An unexposed area of thearea defined by the lines Nos. 25 to 36, which are arrayed in thesub-scan direction, on the recording medium is subjected to theinversion exposure to have patterns of “4” using the second block (spotsNos. 13 to 24), and a solid recording of this area is completed.

(5) At the (M+4)-th rotation of the drum, the recording medium isexposed to have patterns of “5” in FIG. 17(b). Specifically, an areadefined by the lines Nos. 49 to 60, which are arrayed in the sub-scandirection, on the recording medium are subjected to the “thin-outexposure process” using the first block (spots Nos. 1 to 12). Anunexposed area of the area defined by the lines Nos. 37 to 48, which arearrayed in the sub-scan direction, on the recording medium is subjectedto the inversion exposure to have patterns of “5” using the second block(spots Nos. 13 to 24), and a solid recording of this area is completed.

(6) At the (M+5)-th rotation of the drum, the recording medium isexposed to have patterns of “6” in FIG. 7(c). Specifically, an areadefined by the lines Nos. 61 to 72, which are arrayed in the sub-scandirection, on the recording medium are subjected to the “thin-outexposure process” using the first block (spots. Nos. 1 to 12). Anunexposed area of the area defined by the lines Nos. 49 to 60, which arearrayed in the sub-scan direction, on the recording medium is subjectedto the inversion exposure to have patterns of “6”, the exposure beingcarried out using the second block (spots Nos. 13 to 24), and a solidrecording of this area is completed.

Thus, an array of pixels to be thinned out is directed to the downstreamside in the sub-scan direction and to the upstream in the main scandirection. Therefore, the laser energy is not concentrated to thesub-scan lines No. 1 to 24 at a dash, but the same lines arrayed in thesub-scan direction are exposed by plural exposure operations.Accordingly, the load by the heat of the recording medium is small.

Gas that is generated in the exposure operation by the first block(spots Nos. 1 to 12) stagnates in spaces of the thinned-out part of therecording medium. The gas that is generated in the exposure operation bythe second block (spots Nos. 13 to 24) and gas having been stagnated areboth driven to move upstream in the main scan direction and downstreamin the sub-scan direction with the progress of the exposure operation.Finally, those gases are discharged from the ends of the recordingmedium to exterior. As a result, there is no chance that the gasstagnates between the toner layer 240 c and the image receiving layer140 c in the already recorded area, the close contact between the tonerlayer 240 c and the image receiving layer 140 c is maintained, andformation of the image defect based on the spot array is prevented. Thiswill be described later in detail with reference to FIGS. 20(a), 20(b),20(c), 20(d), 20(e), and 20(f).

FIGS. 18(a), 18(b), and 18(c) are diagrams showing a second instance ofthe fifth embodiment in which the exposure process is executed by onlyone exposure operation in a manner that all the spots by the recordinghead are divided into “n” blocks. Specifically, all the spots by therecording head are divided into “n” blocks (preferably, those spots areequally divided). The “thin-out exposure” is carried out by using thefist block of spots. The unexposed area (not the whole) on the recordingmedium is gradually exposed by using the second to (n−1)-th blocks ofspots. Finally, the remaining unexposed area on the recording medium isexposed by using the n-th block of spots.

Description will be given about a case where the spots are divided intothree blocks of spots.

In FIG. 5, 24 number of laser spots are substantially horizontallyarrayed, and a distance between the center of one laser spot to thecenter of another laser spot adjacent to the former is about 10 μm. Ofthose spots, the spots Nos. 1 to 8 form a third block, the spots Nos. 9to 16 form a second block, and the spots Nos. 17 to 24 form a firstblock, and the exposure process is executed by one exposure operation.

(1) FIG. 18(a) showing an exposure state on the recorded recordingmedium at the m-th rotation of the drum, an area defined by the linesNos. 1 to 8 arranged in the sub-scan direction is subjected to the“thin-out exposure process” using the first block (consisting of thespots Nos. 17 to 24) to thereby record patters of “1” on the recordingmedium, as shown.

(2) Subsequently, at the (M+1)-th rotation of the drum, the recordingmedium is exposed to have patterns of “2” in FIG. 18(b). Specifically,an area defined by the lines Nos. 9 to 16 arrayed in the sub-scandirection on the recording medium is subjected to the “thin-out exposureprocess” using the second block (spots Nos. 9 to 16). A half of theremaining part (unexposed area) of the area defined by the lines Nos. 1to 12 on the recording medium is subjected to the “thin-out exposureprocess” using the first block (spots Nos. 17 to 24).

(3) At the (M+2)-th rotation of the drum, the recording medium isexposed to have patterns of “3” in FIG. 8(c). Specifically, an areadefined by the lines Nos. 17 to 24 arrayed in the sub-scan direction onthe recording medium are subjected to the “thin-out exposure process”using the third block (spots Nos. 1 to 8). A half of the remaining part(unexposed area) of the area defined by the lines Nos. 9 to 16, whichare arrayed in the sub-scan direction, on the recording medium issubjected to the “thin-out exposure process” using the second block(spots Nos. 9 to 16). The remaining part (unexposed area) of the areadefined by the lines Nos. 1 to 12 on the recording medium is subjectedto the inversion exposure using the first block (spots Nos. 17 to 24),and a solid recording of this area is completed.

By so doing, gas that is generated in the area defined by the lines Nos.1 to 8 arrayed in the sub-scan direction during the exposure operation,flows to the area defined by the lines Nos. 9 to 16 arrayed in thesub-scan direction. As a result, there is no chance that the gasstagnates in the area defined by the lines Nos. 1 to 8 arrayed in thesub-scan direction.

(4) At the (M+3)-th rotation of the drum, the recording medium isexposed to have patterns of “1” in FIG. 19(a). Specifically, an areadefined by the lines Nos. 25 to 32, which are arrayed in the sub-scandirection, on the recording medium are subjected to the “thin-outexposure process” using the third block (spots Nos. 1 to 8). A half ofthe remaining part (unexposed area) of the area defined by the linesNos. 17 to 24, which are arrayed in the sub-scan direction, on therecording medium is subjected to the “thin-out exposure process” usingthe second block (spots Nos. 9 to 16). The remaining part (unexposedarea) of the area defined by the lines Nos. 9 to 16 on the recordingmedium is subjected to the inversion exposure using the first block(spots Nos. 17 to 24), and a solid recording of this area is completed.

By so doing, gas that is generated in the area defined by the lines Nos.9 to 16, which are arrayed in the sub-scan direction, during theexposure operation, flows to the area defined by the lines Nos. 17 to 24in the sub-scan direction. Accordingly, there is no chance that the gasstagnates in the area defined by the lines Nos. 9 to 16 in the sub-scandirection.

(5) At the (M+4)-th rotation of the drum, the recording medium isexposed to have patterns of “2” in FIG. 19(b). Specifically, an areadefined by the lines Nos. 33 to 40, which are arrayed in the sub-scandirection, on the recording medium are subjected to the “thin-outexposure process” using the third block (spots Nos. 1 to 8). A half ofthe remaining part (unexposed area) of the area defined by the linesNos. 25 to 32, which are arrayed in the sub-scan direction, on therecording medium is subjected to the “thin-out exposure process” usingthe second block (spots Nos. 9 to 16). The remaining part (unexposedarea) of the area defined by the lines Nos. 17 to 24 on the recordingmedium is subjected to the inversion exposure using the first block(spots Nos. 17 to 24), and a solid recording of this area is completed.

By so doing, gas that is generated in the area defined by the lines Nos.17 to 24, which are arrayed in the sub-scan direction, during theexposure operation, flows to the area defined by the lines Nos. 25 to 32in the sub-scan direction. Accordingly, there is no chance that the gasstagnates in the area defined by the lines Nos. 17 to 24 in the sub-scandirection.

(6) At the (M+5)-th rotation of the drum, the recording medium isexposed to have patterns of “3” in FIG. 19©. Specifically, an areadefined by the lines Nos. 41 to 48 arrayed in the sub-scan direction onthe recording medium is subjected to the “thin-out exposure process”using the third block (spots Nos. 1 to 8). A half of the remaining part(unexposed area) of the area defined by the lines Nos. 33 to 40 arrayedin the sub-scan direction on the recording medium is subjected to the“thin-out exposure process” using the second block (spots Nos. 9 to 16).The remaining part (unexposed area) of the area defined by the linesNos. 25 to 32 on the recording medium is subjected to the inversionexposure using the first block (spots Nos. 17 to 24), and a solidrecording of this area is completed.

By so doing, gas that is generated in the area defined by the lines Nos.25 to 32 in the sub-scan direction during the exposure operation, flowsto the area defined by the lines Nos. 33 to 40 in the sub-scandirection. Accordingly, there is no chance for the gas to stagnate inthe area defined by the lines Nos. 25 to 32 in the sub-scan direction.

FIGS. 20(a), 20(b), 20(c), 20(d), 20(e), and 20(f) are diagrams usefulin explaining the direction of the “thin-out exposure process” of thefirst embodiment, and exemplarily showing a case where the exposurepatterns are obliquely recorded. As executed in the first embodiment, apattern to be recorded is slanted to the downstream side in the sub-scandirection and to the upstream side in the main scan direction. Where theso recorded pattern is employed, the exposure operation is performedwhile driving the gas generated in the exposure operation to movedownstream in the sub-scan direction. Consequently, the recordingoperation is performed with no gas stagnation and no density loweredpart.

FIGS. 20(a), 20(b), 20(c), 20(d), 20(e), and 20(f) exemplarily show acase where gas is generated in the two-divided exposure as describedreferring to FIGS. 16(a), 16(b), and 16(c).

(1) FIG. 20(a) shows an exposure state on the recording medium when theexposure operation at the m-th rotation of the drum is completed and anexposure operation at the (m+1)-th rotation of the drum, is ready tostart. An area defined by the lines Nos. 1 to 12 arrayed in the sub-scandirection is subjected to the “thin-out exposure process” using thefirst block (spots Nos. 13 to 24) to thereby record patterns of “1” onthe recording medium, as shown. It is assumed that gas (each denoted ascircle) is generated in the recording operation m-th rotation of thedrum, and the gas stagnates at three positions in the unexposed part onthe recording medium.

(2) FIG. 20(b) shows an exposure state on the recording medium that therecording has reached a position of the 2nd line in the main scandirection at the (M+1)-th rotation of the drum. Of those gasesstagnating at the three positions, the gas located most downstream inthe main scan direction is driven to move in an arrow direction as theresult of the patterns of “2” arrayed in the sub-scan direction, viz.,it is moved to an unexposed part located downstream in the sub-scandirection and upstream in the main scan direction. The reason for thisis that the gas cannot flow into the exposed pixel spaces. Of thosegases at the three positions, the two gases positioned upstream in themain scan direction are not subjected to the exposure operation in thesub-scan direction, and therefore those two gases still stagnate at thesame positions.

Also in the second exposure operation, gas is generated sometimes. Thegas generated is also driven to move to the unexposed part of therecording medium, although it is not illustrated.

(3) FIG. 20(c) shows an exposure state on the recording medium that therecording has reached a position of the 6th row in the main scandirection at the (M+1)-th rotation of the drum. With the progress of theexposure operation for the patterns of “2”, the two gases locateddownstream in the sub-scan direction on the recording medium are drivento move to an unexposed part thereof located downstream in the sub-scandirection and upstream in the main scan direction, and those gases arecombined to form a large mass of gas.

(4) FIG. 20(d) shows an exposure state on the recording medium that therecording has reached a position of the 10th row in the main scandirection at the (M+1)-th rotation of the drum. By the exposureoperation recording a pattern of “2”, the mass of gas has driven to moveoutside an area (defined by the lines Nos. 1 to 12 arrayed in thesub-scan direction) to be exposed at the m-th rotation of the drum.

(5) FIG. 20(e) shows an exposure state on the recording medium that therecording has reached a position of the 14th row in the main scandirection at the (M+1)th rotation of the drum. The mass of gas remainsstagnating at the unexposed part of the recording medium. By theexposure operation of recording patterns of “2” in the sub-scandirection, of the already existing three gases, the gas located mostupstream in the main scan direction is driven to move to an unexposedpart located downstream in the sub-scan direction and upstream in themain scan direction.

(6) FIG. 20(f) shows an exposure state on the recording medium that therecording has reached a position of the 17th row in the main scandirection at the (M+2)-th rotation of the drum. By the exposureoperation of recording patterns of “3” arrayed in the sub-scandirection, the mass of gas having stagnated in FIG. 20(e) is driven tomove to an unexposed part located downstream in the sub-scan directionand upstream in the main scan direction. In this way, the gasesgenerated in the exposure operation at the m-th rotation of the drum,are driven to move to the ends of the recording medium, and dischargedoutside from the ends of the recording medium.

When the exposure pattern is so configured and the exposure patterns arearrayed as mentioned above, as shown in FIG. 20(f), there is no chancethat the gas stagnates between the toner layer 240 c and the imagereceiving layer 140 c in the recorded area, the close contact betweenthe toner layer 240 c and the image receiving layer 140 c is maintained,and formation of the image defect based on the spot array is prevented.

The exposure method effectively operates when the dot area rate is 70%or higher, particularly for the solid part (where the dot area rate is100%).

As described above, one of the features of the invention is that anarray of unexposed pixels to be thinned out on the recording medium aredirected to the downstream side as viewed in the sub-scan direction andthe upstream side in the main scan direction. Where those pixels arearrayed in a direction opposite to that of the above-mentioned one, itis impossible to produce such useful effects produced.

Next, the “thin-out exposure process” of the invention will be describedby taking a called “solid recording” as an example.

FIGS. 23(a), 23(b), 23(c), 24(a), 24(b), and 24(c) show a “thin-outexposure process” according to the sixth embodiment of this invention. Afirst exposure operation is performed in a thin-out manner, by movingthe recording head to a position near the end of the sub-scan (FIGS.23(a), 23(b), and 23(c)). Then, the recording head is returned to aposition near the original position of the sub-scan, and an exposureoperation is performed again, while forming inverted patterns (FIGS.24(a), 24(b), and 24(c)).

(1) FIG. 23(a) shows an exposure state on the recorded recording mediumfixed to the drum at the m-th rotation of the drum. In the figure,patterns of “1”s are exposed pixels recorded at the m-th rotation of thedrum, and other white squares are unexposed pixels. Specifically, at them-th rotation of the drum in the first exposure operation, an areadefined by the lines Nos. 1 to 24 arrayed in the sub-scan direction areexposed in a thin-out manner by using the spots Nos. 1 to 24, to havepatterns of “1” of FIG. 23(a).

As seen from figure, in the operation of exposing and recording the fistline at the m-th rotation of the drum (FIG. 23(a)) in the first exposureoperation, the spots Nos. 1 to 24 (FIG. 5), the spots Nos. 24, 23, 22,18, 17, 16, 12, 11, 10, 6, 5, 4 are driven to expose the pixels of thelines Nos. 1, 2, 3, 7, 8, 9, 13, 14, 15, 19, 20, 21 arrayed in thesub-scan direction.

In the exposure operation in which at the m-th rotation of the drum, thedrum slightly rotates and the 2nd line is positioned under the spotsNos. 1 to 24, the spots Nos. 23, 22, 21, 17, 16, 15, 11, 10, 9, 5, 4, 3of those spots Nos. 1 to 24 are driven to expose the pixels of the linesNos. 2, 3, 4, 8, 9, 10, 14, 15, 16, 20, 21, 22 arrayed in the sub-scandirection.

Further, in the exposure operation in which at the m-th rotation of thedrum, the drum slightly rotates and the 3rd line is positioned under thespots Nos. 1 to 24, the spots Nos. 22, 21, 20, 16, 15, 14, 10, 9, 8, 4,3, 2 of those spots Nos. 1 to 24 are driven to expose the pixels of thelines Nos. 3, 4, 5, 9, 10, 11, 15, 16, 17, 21, 22, 23 arrayed in thesub-scan direction.

Subsequently, as the line number of the lines to be exposed at the samenumber of rotations of the drum increases, the spots to be driven aresuccessively shifted in the sub-scan direction. With this, an array ofpixels to be thinned out is directed to the downstream side in thesub-scan direction and to the upstream side in the main scan direction.

In the above description, for ease of explanation, the recording head isnot moved in the sub-scan direction during one rotation of the drum.Actually, however, the recording head is also moved in the sub-scandirection during one rotation of the drum. A relationship between thespots Nos. 1 to 24 and the line numbers of the lines arrayed in thesub-scan direction is shifted by an amount of the head movement to thesub-scan direction.

(2) Subsequently, at the (m+1)-th rotation of the drum in the firstexposure operation, an area defined by the lines Nos. 25 to 48 arrayedin the sub-scan direction is exposed in a thin-out manner by using thespots Nos. 1 to 24, to have patterns of “2” of FIG. 23(b). Thethinning-out manner is the same as of “1” of FIG. 23(a).

(3) Then, at the (m+2)-th rotation of the drum in the first exposureoperation, an area defined by the lines Nos. 49 to 72 arrayed in thesub-scan direction are exposed in a thin-out manner by using the spotsNos. 1 to 24, to have patterns of “3” of FIG. 23(c). The thinning-outmanner is the same as of “1” of FIG. 23(a). Subsequently, the recordinghead is moved to a position near the end position of the sub-san, whilerepeating the sequence of exposure operations mentioned above, and thefirst exposure operation ends.

(4) After the first exposure operation (sub-scanning operation by therecording head) ends, the recording head is returned to the originalposition of the sub-scan, and the recording by the second exposureoperation is performed as shown in FIGS. 24(a), 24(b), and 24(c).

In (FIG. 24(a), in the exposure of the 1st line at the m-th rotation ofthe drum, the spots Nos. 21, 20, 19, 15, 14, 13, 9, 8, 7, 3, 2, 1 of thespots Nos. 1 to 24 are driven to expose the pixels of the lines Nos. 4,5, 6, 10, 11, 12, 16, 17, 18, 22, 23, 24 arrayed in the sub-scandirection, and the remaining part, which was thinned out in the firstexposure operation, is exposed to have patterns of “6” in the figure.

(5) At the (m+1)-th rotation of the drum in the second exposureoperation, as shown (FIG. 24(b)), an area defined by the lines Nos. 25to 48 arrayed in the sub-scan direction, i.e., the remaining partsthinned out in the fist exposure operation, are exposed by using thespots Nos. 1 to 24, to have patterns of “7” in the figure.

(6) At the (m+2)-th rotation of the drum in the second exposureoperation (FIG. 24(c)), an area defined by the lines Nos. 49 to 72arrayed in the sub-scan direction, i.e., the remaining parts thinned outin the fist exposure operation, are exposed by using the spots Nos. 1 to24, to have patterns of “8” in

Thus, the laser energy is not concentrated to the sub-scan lines No. 1to 24 at a dash, but the same lines arrayed in the sub-scan directionare exposed by plural exposure operations. Accordingly, the load by theheat of the recording medium is small.

Gas that is generated in the first exposure operation stagnates in thespaces of the thinned-out part of the recording medium. The gas that isgenerated in the second exposure operation and gas having been stagnatedare both driven to move upstream in the main scan direction anddownstream in the sub-scan direction with the progress of the exposureoperation. Finally, those gases are discharged from the ends of therecording medium to exterior. As a result, there is no chance that thegas stagnates between the toner layer 240 c and the image receivinglayer 140 c in the already recorded area, the close contact between thetoner layer 240 c and the image receiving layer 140 c is maintained, andformation of the image defect resulting from the spot array isprevented. This will be described in detail in the description of thesecond embodiment of the invention.

In the first instance of the first embodiment, the description has madeabout a case where the “thin-out exposure process” is executed by twoexposure operations, viz., the “thin-out exposure process” is executedby repeating the exposure operation two times, or the exposure operationfor the “thin-out exposure process” is divided into two operations.However, it will readily be understood that the number of divisions ofthe exposure operation for the “thin-out exposure process” is notlimited to 2, but may be 3 or larger.

Further, in the description, after the first exposure operation ends,the recording head is returned to a position near the original positionin the sub-scan direction. In alternative, the recording head mayperform the second exposure operation, while the recording head returnsfrom the end position of the sub-scan direction to near the originalposition.

FIGS. 25(a), 25(b), 25(c), 25(d), 25(e) and 25(f) are diagrams useful inexplaining the thinning-out direction in the “thin-out exposure process”of the second embodiment of the invention.

In the second embodiment of the invention, the recording apparatus 1 ischaracterized by that the exposure patterns are obliquely arranged.

As executed in the first embodiment, a pattern to record is slanted tothe downstream side in the sub-scan direction and to the upstream sidein the main scan direction.

By so slanting the patterns, the exposure operation is performed whiledriving the gas generated in the exposure operation to move downstreamin the sub-scan direction.

Accordingly, the recording operation is performed with no gas stagnationand no density lowered part.

This specific example will be described with reference to FIGS. 25(a),25(b), 25(c), 25(d), 25(e) and 25(f) showing a process in which afterthe first exposure operation (the sub-scanning operation by therecording head) ends, the recording head returns to a position near theoriginal point of the sub-scan, and the recording by a second exposureoperation is performed as shown in FIG. 24(a).

FIG. 25(a) shows a state on the recording medium before the secondexposure operation starts. In the figure, gas (each denoted as a circle)that is generated in the recording of patterns of “1” in first exposureoperation, stagnates in the unexposed part on the recording medium.

In FIG. 25(b), the 1st line in the unexposed part is exposed forrecording by the second exposure operation. At this time, since thealready existing gas (denoted as a circle) cannot flow into the exposedpixel spaces, it is moved in a direction of an arrow, i.e., to anunexposed part. Further, in FIG. 25(c), a position of the 2nd line inthe main scan direction of the unexposed part is exposed by the secondexposure operation. At this time, the already existing gas and gasgenerated in the second exposure operation are also moved to theunexposed part of the recording medium.

As the operation of exposing the lines in the unexposed part progresses,as shown in FIG. 25(d), the already existing gas and gas generated inthe second exposure operation are likewise moved to the unexposed partlocated downstream in the sub-scan direction and upstream in the mainscan direction.

And, in FIG. 25(e), the gas having been driven to move to the ends ofthe recording medium is discharged outside from the ends of therecording medium.

When the exposure pattern is so configured and the exposure patterns arearrayed as mentioned above, as shown in FIG. 25(f), there is no chancethat the gas stagnates between the toner layer 240 c and the imagereceiving layer 140 c in the recorded area, the close contact betweenthe toner layer 240 c and the image receiving layer 140 c is maintained,and formation of the image defect resulting from the spot array isprevented.

The exposure method effectively operates when the dot area rate is 70%or higher, particularly for the solid part (where the dot area rate is100%).

FIG. 26 is a block diagram showing a process in which an image signalcoming from a computer is processed and an image signal to be applied tothe recording head is generated.

1) An image signal coming from a computer is input to an image signalinput section in the controller section. An image signal from thecomputer takes a form as shown in FIG. 27(a).

2) The image signal input section takes out an image signal of the m-throtation of the drum from the image signal coming from the computer, andsends it to a pattern signal processor part.

3) The pattern signal processor part computes the image signals of them-th rotation of the drum, and sends it to an image signal outputsection.

4) The image signal output section drives the recording head forexposure in accordance with the incoming image signals.

FIGS. 27(b) and 27(c) are diagrams showing a process in which the imagesignal as shown in FIG. 27(a) is exposed in a thin-out manner andrecorded according to the invention. FIG. 27(b) shows positions (in thearea defined by lines Nos. 1 to 24 in the sub-scan direction) on therecording medium to be recorded by the first exposure operation. Asseen, the recording medium is exposed in thin-out patterns, which areslanted to the downstream side in the sub-scan direction and to theupstream side in the main scan direction.

FIG. 27(c) shows positions (in the area defined by lines Nos. 1 to 24 inthe sub-scan direction) on the recording medium to be recorded by thesecond exposure operation. This is for exposing the thinned-out,unexposed part thinned in FIG. 27(b), and is a pattern slanted to thedownstream side in the sub-scan direction and to the upstream side inthe main scan direction.

As the result of performing the first and second exposure operations,the energy is dispersed, and the gas is driven to move outside therecording medium, so that the solid recording is performed while beingfree from the image defect.

In the embodiments mentioned above, the recording medium fixing memberof the outer drum type is presented by way of example. It may be of theinner drum type in which the recording medium is fixed to the incurvedsurface or the inner peripheral surface of a cylinder, and a laser beamis emitted, for recording, from the center of incurved surface or thecylinder. A recording device of the type in which a laser beam is movedin the main scan direction, and the recording medium is transported inthe sub-scan direction by means of a transporting mechanism, may also beused instead of the drum. The recording medium fixing member may be ofthe flat table type in which it is movable in the main scan direction.While the laser light spots one dimensionally arrayed are used in theembodiments, the laser beam spots two dimensionally arrayed may also beused instead.

As seen from the foregoing description, in an image recording method andapparatus of the invention, in a first exposure operation in which therecording head is moved from the position near the original point of thesub-scan to the position near the end point of the sub-scan,image/character data is exposed in a thin-out manner, and in a secondexposure operation and the subsequent ones, the pixels in thethinned-out, unexposed part are successively exposed. Therefore, gasgenerated at a local part or area of the recording medium is moved tothe downstream in the sub-scan direction and the upstream side in themain scan direction, with movement of the recording head. The gas isforced to flow to the unexposed part or area, and finally dischargedoutside the recording medium. As a result, the gas stagnation betweenthe toner layer and the image receiving layer at the already recordedarea or part is prevented.

1-15. (canceled)
 16. An image recording method executed by a recordingapparatus including a recording medium fixing member for fixing arecording medium formed by coupling together a toner layer of a transferfilm as a heat mode sensitive material and an image receiving layer of areceiver film in a layering manner and having a plurality of spotsarrayed on a surface thereof, and a recording head capable ofirradiating for exposing the recording medium, the method comprising thesteps of: recording for recording a desired image on the recordingmedium by the recording head exposing the recording medium alongimage/character data with letting the recording medium relatively movein a main scan direction between the recording medium fixing member andthe recording head as well as letting the spots relatively move in asub-scan direction; exposing for exposing pixels on the recording mediumin the sub-scan direction by relatively moving the recording head from aposition near the original point of the sub-scan to a position near theend of the sub-scan; and dividing all the spots into “n” number ofblocks; wherein a first block of the divided spots is used for exposingpixels on the recording medium with thinning out a part of the pixels,from second to (n−1)th blocks of the divided spots are simultaneouslyused for gradually exposing pixels in unexposed part on the recordingmedium, nth block of the divided spots is also simultaneously used forexposing all the remaining pixels in the unexposed part, and at thistime an array of pixels to be thinned out is directed to the downstreamside in the sub-scan direction and to the upstream in the main scandirection, wherein n is an optional positive integer of 2 or larger. 17.An image recording apparatus comprising: a recording medium fixingmember for fixing a recording medium formed by coupling together a tonerlayer of a transfer film as a heat mode sensitive material and an imagereceiving layer of a receiver film in a layering manner and having aplurality of spots arrayed on a surface of the recording medium; arecording head capable of irradiating for exposing the recording mediumalong image/character data in order to record a desired image on therecording medium, performing a first exposure operation by movingrelative to the recording medium in a main scan direction simultaneouslywith moving of the plurality of spots in sub-scan direction, which isorthogonal to the main scan direction, and performing a second exposureoperation by moving in the sub-scan direction; and wherein all the spotsare divided into “n” number of blocks, the pixels on the recordingmedium are thin-out exposed by using the first block of spots, and atthe same time the pixels in an unexposed part on the recording medium isgradually exposed by using the 2nd to (n−1)th blocks, the remainingpixels in the unexposed part are all exposed by using the n-th block,and at this time, an array of pixels to be thinned out is directed tothe downstream side in the sub-scan direction and to the upstream in themain scan direction.
 18. The image recording apparatus according toclaim 17, wherein the thin-out exposure operation is performed such thatthe line number of a line of those lines arrayed in the sub-scandirection of an exposed pixel of a row is the same as or the precedingor succeeding line number of a line of those lines arrayed in thesub-scan direction of an exposed pixel of the subsequent row.
 19. Theimage recording apparatus according to claim 17, wherein a percentage ofthe thinned out lines at the exposure by said block of spots is 20% to80% of the whole image/character data to be exposed.
 20. The imagerecording apparatus according to claim 17, wherein at the exposure bythe n-th block, a percentage of the image/character data other than thatexposed by the 1st to (n−1)th blocks is 20% or higher of the wholeimage/character data to be exposed.
 21. An image recording methodexecuted by a recording apparatus including a recording medium fixingmember for fixing a recording medium formed by coupling together a tonerlayer of a transfer film as a heat mode sensitive material and an imagereceiving layer of a receiver film in a layering manner and having aplurality of spots arrayed on a surface thereof, and a recording headcapable of irradiating for exposing the recording medium, the methodcomprising the steps of: recording for recording a desired image on therecording medium by the recording head exposing the recording mediumalong image/character data with letting the recording medium relativelymove in a main scan direction between the recording medium fixing memberand the recording head as well as letting the spots relatively move in asub-scan direction; first exposing for exposing pixels on the recordingmedium in the sub-scan direction by relatively moving the recording headfrom a position near the original point of the sub-scan to a positionnear the end of the sub-scan; second exposing for exposing pixels inunexposed area on the recording medium; and repeating the step of secondexposing; wherein, in the step of first exposing, image/character datais exposed in a thin-out manner, and wherein, in the steps of secondexposing and repeating, the pixels in the thinned-out, unexposed partare successively exposed.
 22. An image recording apparatus comprising: arecording medium fixing member for fixing a recording medium formed bycoupling together a toner layer of a transfer film as a heat modesensitive material and an image receiving layer of a receiver film in alayering manner and having a plurality of spots arrayed on a surface ofthe recording medium; a recording head capable of irradiating forrecording a desired image on the recording medium by exposing alongimage/character data with moving relative to the recording medium in amain scan direction, at the same time the plurality of spots are movingin sub-scan direction orthogonal to the main scan direction, performinga first exposure operation for exposing pixels on the recording mediumby moving in the sub-scan direction, performing a second exposingoperation for exposing pixels of unexposed area on the recording medium,and repeating the second exposing operation; and an exposure controllerdevice controlling the recording head so that, in a first exposureoperation, image/character data is exposed in a thin-out manner, and ina second exposure operation and the subsequent ones, the pixels in thethinned-out and unexposed part are successively exposed.
 23. The imagerecording device according to claim 22, wherein in said first exposureoperation, after said recording head reaches a position near the end ofthe sub-scan in the first exposure operation and returns to a positionnear the original point of the sub-scan, the pixels in said unexposedarea not having been exposed in the preceding exposure operation areexposed R times, and wherein R is a optional positive integer.
 24. Theimage recording apparatus according to claim 22, wherein in said firstexposure operation, after said recording head reaches said position nearthe end of the sub-scan in the first exposure operation, said recordinghead returns to said position near the original point of the sub-scanwhile exposing the pixels in said unexposed area not having been exposedin the preceding exposure operation.
 25. The image recording apparatusaccording to claim 22, wherein at the R-th exposure by said recordinghead, said recording head may expose the remaining image/character dataother than the image/character data having been exposed in said first to(R−1)th exposure operations.
 26. The image recording apparatus accordingto claim 22, wherein at the first exposure, a percentage of thin-outexposing to the whole image/character data to be exposed is 20% to 80%.27. The image recording apparatus according to claim 22, wherein at theR-th exposure operation, a percentage of said image/character data otherthan the image/character data having been exposed in said first to(R−1)th exposure operations, to the whole image/character data to beexposed is 20% or higher.
 28. The image recording apparatus accordingclaim 22, wherein an array of said pixels to be thinned out is directedto the downstream side in the sub-scan direction, and to the upstreamside in the main scan direction.
 29. The image recording apparatusaccording to claim 28, wherein the thin-out exposure operation isperformed such that the line number of a line of those lines arrayed inthe sub-scan direction of an exposed pixel of a row is the same as orthe preceding or succeeding line number of a line of those lines arrayedin the sub-scan direction of an exposed pixel of the subsequent row.